Flat display tube with a compact electron gun assembly



May 20, 1969 s, HAVN ET AL FLAT DISPLAY TUBE WITH A COMPACT ELECTRON GUN ASSEMBLY Sheet Filed March 27. 1967 PRIOR ART osnsc non SOURCE OF HORIZON TAL SIGNALS l NVENTORS SVEND E. HAVN MOOSHI R. NAMORDI.

BY '1). T EIR ATTORNEY.

May 20, 1969 s, HAVN ETAL 3,445,716

FLAT DISPLAY TUBE WITH A COMPACT ELECTRON GUN ASSEMBLY Filed March 27. 1967 Sheet 5 or 4 SOURCE OF HORIZONTAL v-IO DEFLEOTION SIGNALS SOURCE OF HORIZONT INVENTORS SVEND E. HAVN MOOSHI R. NAMORDI,

THEIR ATTORNEY.

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FLAT DISPLAY TUBE WITH A COMPACT ELECTRON GUN ASSEMBLY Filed March Sheet 4 of4 SOURCE OF HORIZON TAL DEF LE 0 TION SIGNALS FIG.8.

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T EIR ATTORN United States Patent 0 US. Cl. 315-18 7 Claims ABSTRACT OF THE DISCLOSURE To reduce the overall dimensions of a shallow cathode ray tube system including target area, a vertical deflection section, a horizontal deflection section comprising magnetostatic and magnetodynamic pole plates, and an electron gun section including an electron gun and an electron beam reflecting means aligned with an axis parallel to the vertical axis of deflection. The reflecting means may comprise various alternatives including magnetostatic pole plates joined by a magnet, magnetostatic pole plates joined by a magnet and encircled by a magnetodynamic deflection coil, or electrostatic deflection plates, with each pair of plates parallel, and having parallel edges to produce parallel lines of flux between the plates.

Background of the invention The invention relates to an image display stystem utilizing a relatively shallow cathode ray tube, and more specifically, it relates to a compact electron gun arrangement for a shallow cathode ray tube.

In the shallow cathode ray tube systems of the prior art, the overall depth of the tube has been reduced but the overall planar dimensions parallel to the screen have been increased in order to accommodate the electron gun. The net result has been an increase in the overall width of the cathode ray tube in a plane parallel to the target area. Since the shallow cathode ray tube finds its application in those areas where overall minimal dimensions are of the utmost importance, it is desirable to reduce the overall width of the tube as well as the overall depth.

In those shallow cathode ray tube systems in which the electron gun has been compactly positioned with respect to the target area, electron beam reflecting means of one form or another have been utilized with less than satisfactory results. These less than satisfactory results have occurred since the electron beam has been subjected to a converging or diverging influence by the reflecting means rather than retaining a collimated characteristic to allow uniform scanning by the horizontal and vertical deflection means. The end result was a less than satisfactory display.

Summary of the invention It is an object of this invention to provide a shallow cathode ray tube of minimal overall dimensions.

It is a still further object of this invention to provide a shallow cathode ray tube in which the achievement of overall dimensions does not affect the quality of the display.

Briefly stated, and in accordance with certain aspects of this invention, we provide a flat tube display utilizing an improved shallow cathode ray tube comprising an electron target with a pair of orthogonal axes in the plane thereof, a first deflection section with means providing deflection along a first orthogonal axis of the pair and a second deflection section with means providing deflection along a second orthogonal axis of the pair. The electron beam source has a central axis substantially parallel to one of the pair and aligned with an electron beam reflecting "ice means producing parallel lines of flux of mutually equal magnitude. The reflecting means is positioned so as to achieve reflection of the electron beam into the first deflection section.

Brief description of the drawings The specification concludes with claims particularly pointing out and distinctly claiming the subject matter which we regard as our invention. The invention may also be understood from the following description taken in connection with the accompanying drawings in which:

FIGURE 1 is a front view of the shallow cathode ray tube system of the prior art;

FIGURE 2 is a front view of a preferred embodiment of the invention in a shallow cathode ray tube system;

FIGURE 3 is a side view of the shallow cathode ray tube system of FIGURE 2;

FIGURE 4 is a front view of a first alternative embodiment of the invention in a shallow cathode ray tube system;

FIGURE 5 is a side view of the shallow cathode ray tube system of FIGURE 4;

FIGURE 6 is a front, partial cutaway view of a second alternative embodiment of the invention in a shallow cathode ray tube system;

FIGURE 7 is a partial view of the shallow cathode ray tube of FIGURE 6 taken along line 1--1; and

FIGURE 8 is a side view of the shallow cathode ray tube system shown in FIGURE 6.

Description of the preferred embodiments By way of explanation, the shallow cathode ray tube system of the prior art as shown in FIGURE 1 and those embodiments of the invention as shown in FIGURES 2, 4, and 6 have been subdivided into an image section bracketed and designated by the letter I, a vertical deflection section bracketed and designated by the letters VD, a horizontal deflection section bracketed and designated by the letters HD, and an electron gun section bracketed and designated by the letters EG. The image section I may be constructed in accordance with the disclosure in US. Patent No. 3,177,395 which is assigned to the assignee of the present invention. Various alternatives may be used in the vertical deflection section VD and the vertical deflection section disclosed in the above-mentioned patent is an example. Only the sections HD and EG will be described in considerable detail herein since these sections in combination provide an improvement in shallow cathode ray tube systems of the prior art.

In the prior art as shown in FIGURE 1, a protruding electron gun 2 projects a beam of electrons 3 between pole plates 4, only one of which is visible in this view. The magnetic field between pole plates 4 is accomplished in a well-known manner by a yoke 6, a deflection coil 8, and a source 10 of horizontal deflection signals. The magnetic field causes the beam to scan a plane parallel to the paper from a first extreme position 3' to a second extreme position 3". Parallel and spaced pole plates 12, only one of which is visible in this view, are mounted adjacent the outside wall of the horizontal deflection section HD. The pole plates 12 are joined at the ends thereof by a magnet 14 and so shaped that the beam of electrons emerges along parallel vertical and planar paths regardless of where the beam first enters the space between the pole plates 12. The collimated, horizontally scanned beam thus formed enters the vetrical deflection section VD and scans the target 16. For convenience, an orthogonal coordinate system comprising a vertical axis V V and a horizontal axis H -H have been superimposed upon the target 16. The vertical axis V -V and the horizontal axis H H correspond to the axis on which vertical deflection is achieved by a vertical deflection section VD and horizontal deflection is achieved by the horizontal deflection section HD, respectively. Although the terms horizontal and vertical have been adopted to give orientation to a discussion of dimensions and deflection, these words have been chosen for the sake of orientation alone and should not be construed to limit the nature of the first deflection section so designated as horizontal and the second deflection section so designated as vertical.

As may be seen, an election gun encasement 18 protrudes from the horizontal deflection section HD a considerable distance, essentially in a direction parallel to the horizontal axis H H Although the positioning of the electron gun 2 in the encasement 18 has allowed a reduction in the depth of the cathode ray tube system as measured in a direction normal to the image section I, the overall dimension along the horizontal axis H -H has been substantially increased. In contrast, an embodiment of the invention allows the electron gun 2 in the encasement 18 to be repositioned and thereby effect an overall reduction in width.

In order to achieve an effective comparison of the preferred embodiment as shown in FIGURE 2 and the prior art as discussed with regard to FIGURE 1, the image section I, the vertical deflection section VD, and the horizontal deflection section HD remain identical. However, the encasement 18 has been repositioned such that the central axis C C of the electron gun 2 is parallel with the axis V V and aligned with an opening in an enclosure neck 19. A reflecting means for the beam 3 comprising pole plates 20, only one of which is seen in FIG- URE 2, and a magnet 21 joining one pair of ends of the pole plates 20 are provided to redirect the electron beam 3 2115) the pole plates 4 of the horizontal deflection section However, it is not enough to merely redirect the electron beam 3 to the pole plates 4. Rather, redirection must occur without creating a convergence or divergence of the electrons within the beam after reflection. Divergence and convergence may be avoided as long as the reflecting means 20 produces parallel lines of flux normal to the plane defined by the axes V V and H -Hg to assure the path length of each electron in the electron beam 3 will be equal while it is subject to the lines of flux generated by the reflecting means. A shown in FIGURE 2, the parallel lines of flux are achieved by the pole plates 20 which must, of necessity, have parallel edges of incidence 23 and reflection 24. Of course, the magnitude of the parallel lines of flux and the angles of incidence to and reflection from the reflecting means comprising the pole plates 20* must be properly chosen in order to assure I entry of the electron beam 3 at the central axis of the pole plates 4.

FIGURE 3 illustrates a side view wherein both of the pole plates 4 and both of the pole plates 20 are shown.

The neck 19 is shown as inserted between the pole plates 4 and the pole plates 20 to provide an enclosed path for the electron beam 3 from the electron gun 2 positioned within the encasement 18 to the horizontal deflection section HD.

The first alternative embodiment of FIGURES 4 and 5 utilizes a structure identical to that of FIGURE 2 except for the absence of the pole plates 4 with the yoke 6 and the addition of a superpositioned magnetodynamic field upon the magnetostatic field produced by the magnet 21. In order to provide the superposition, the deflection coil 8 encircles the magnet 21 and is supplied by the source of horizontal deflection signals 10. As a result, the electron beam 3 will enter the pole plates 12 in various positions although always vertically collimated due to the equal path lengths of all electrons in the beam 3 between the pole plates 20. This embodiment not only allows the overall planar dimensions to be reduced but simultaneously provides a means for horizontal sweep. FIGURE 5 discloses the nature of the deflection coil 8 and the encircled magnet 21.

FIGURE 6 discloses the second alternative embodiment of the invention wherein the shallow cathode ray tube system of FIGURE 2 is utilized except for the replacement of the pole plates 20 and the magnet 21 by an electrostatic reflecting means. As shown in the cutaway view of FIGURE 6, the electrostatic reflecting means, comprising a first positive plate 27 and a parallel distortion eliminating screen 33 attached and electrically connected thereto, is angularly positioned between the electron gun 2 and the pole plates 4. A second, negative plate 28 is positioned beneath the positive plate 27 and connected thereto by uniform planar resistive connections 29 thereby creating a region that exerts a uniform force upon the electron in a directional normal to the plates 27 and 28. In order to achieve the uniform force, the resistive connections 29 extend the full length of the plates 27 and 28. In addition, the plate 27 which contains an elongated aperture 32 is guarded by the distortion eliminating screen 3 3 through which the electron beam 3 may pass as shown in FIGURE 7. Upon entry into the region between the positive plate 27 and the negative plate 28, the beam 3 proceeds toward the negative plate 28, is reflected, and emerges from the aperture 32 in a collimated condition.

FIGURE 8 discloses a side view of the shallow cathode ray tube system wherein the neck 19 is cut away as shown in FIGURE 6 to more fully reveal the lower negative plate 28 and the resistive connections 29.

It is appreciated that the magnitude of the magnetic field between the plates 20 controls the cross sectional area of the electron beam 3 thereby providing a function in addition to reflection. The cross sectional area is increased when the field is decreased and decreased when the field is increased. This relationship allows a funneling to occur without the addition of a specific electrode for that purpose.

It is further appreciated that the magnetostatic field between the plates 20 may be achieved by magnetism produced by a DC current flowing through a coil rather than that produced by a permanent magnet.

Finally, the word parallel should not be construed in a strict sense since it is only necessary that any too given lines of flux be maintained in equidistantly spaced relationship. For example, it is possible that the lines of flux could be arcs of equal radius since the individual paths of individual electrons would still be equal as they pass through the reflecting means thereby achieving the desired collimating effect.

Although specific embdoiments of the invention have been shown and described, it is not desired that the invention be limited to the particular form shown and described, and it is intended by the appended claims to cover all modifications within the spirit and scope of the invention.

What is claimed as new and desired to be secured by Letters Patent of the United States is:

1. In a shallow cathode ray tube comprising an electron target defining a plane of orthogonal axes, a first deflection section with means providing deflection along a first orthogonal axis and a second deflection section adjacent said target with means providing deflection along the second of the orthogonal axes, the improvement comprising:

(a) a source of electrons generating an electron beam with a central axis substantially parallel to the second orthogonal axis, said source positioned adjacent the first deflection section; and

(b) pole plates aligned with the central axis for producing a magnetostatic field and a magnetodynamic field including flux lines normal to the plane of the orthogonal axes, said pole plates serving as a source of horizontal deflection.

2. The improved shallow cathode ray tube as recited in claim 1 wherein said pole plates are formed such that the path length of each electron in the electron beam is equal while it is subject to the field between said plates.

3. The improved shallow cathode ray tube as recited in claim 2 wherein said pole plates include edges which are parallel such that the electron beam is incident upon and reflected from the field produced between the respective parallel edges.

4. In a shallow cathode ray tube comprising an electron target defining a plane of orthogonal axes, .a first deflection section with means providing deflection along a first orthogonal axis and a second deflection section adjacent said target with means providing deflection along the second of the orthogonal axes, the improvement comprising:

(a) a source of electrons generating an electron beam with a central axis substantially parallel to the second orthogonal axis, said source positioned adjacent the first deflection section; and

(b) parallel pole plates aligned with the central axis for producing parallel lines of flux for deflecting the electron beam in a plane parallel to the plane defined by the orthogonal axes, said pole plates being formed such that the path length of each electron in the beam while it is subject to the lines of flux between the plates is equal.

5. The improved shallow cathode ray tube as recited in claim 4 in which said pole plates produce a magnetostatic field and include parallel edges such that the electron beam is incident upon and reflected from the field produced between the respective parallel edges.

6. The improved shallow cathode ray tube as recited in claim 4 wherein said plates produce an electrostatic field and are normal to the plane of the orthogonal axes.

7. The improved shallow cathode ray tube as recited in claim 6 wherein one of the plates includes an aperture through which the beam passes and a distortion eliminating screen mounted parallel thereto.

References Cited UNITED STATES PATENTS 8/1956 Longini 315l8 3/1960 Aiken et al 31518 

